JP2006505953A - Laser scanning apparatus and heat treatment method - Google Patents

Abstract

  An apparatus and method for heat treating a substrate using scanned laser radiation is disclosed. The apparatus includes a continuous radiation source and an optical system that forms an image on the substrate. The image is scanned with respect to the surface of the substrate such that each point of the treated area receives a pulse of radiation sufficient to heat treat the area.

Description

Background of the Invention

  The present invention relates to an apparatus and method for heat-treating a substrate, and more particularly, to an apparatus and method for heat-treating a semiconductor substrate including an integrated device or an integrated circuit.

  Integrated circuit (IC) fabrication involves subjecting a semiconductor substrate to many processes such as photoresist coating, photolithography exposure, photoresist development, etching, polishing, and heating or “thermal processing”. It is. In certain applications, the heat treatment is performed to activate dopants in the doped regions (eg, source / drain regions) of the substrate. The heat treatment includes various heating (and cooling) techniques such as rapid thermal annealing (RTA) and laser heat treatment (LTP). If a laser is used to perform the heat treatment, this technique may be referred to as “laser processing” or “laser annealing”.

  Various techniques and apparatus for laser processing of semiconductor substrates are known and used in the integrated circuit (IC) manufacturing industry. The laser treatment is preferably performed in a single cycle in which the temperature of the material to be annealed is raised to the annealing temperature and then lowered to the starting (eg, ambient) temperature.

  If the heat treatment cycle required for activation or annealing can be maintained at 1 millisecond (msec) or less, the IC performance can be greatly improved. Thermal cycle times of less than 1 microsecond (μsec) are easily obtained using radiation from a pulsed laser that spreads uniformly over one or more circuits. An example of an apparatus for performing laser heat treatment using a pulsed laser source is described in US Pat. No. 6,366,308B1, entitled “Laser Thermal Processing Apparatus and Method”. However, the shorter the radiation pulse, the shallower the region that can be heat treated, and the more likely it will be that the circuit element itself will undergo a large temperature change. For example, a polysilicon conductor on a thick field oxide isolation region is heated much more rapidly than a shallow junction on the surface of a silicon wafer.

By using longer radiation pulses, a more uniform temperature distribution can be obtained. This is because, in the pulse interval, the heating depth is larger, the time for the lateral heat conduction is longer, and the temperature of the entire circuit is equalized. However, it is impractical to make the laser pulse width longer than 1 microsecond over a circuit area of 5 cm ² or more. This is because the energy per pulse becomes too high, and the lasers and associated power supplies required to supply such high energy are very large and expensive.

  An alternative approach to using pulsed radiation is to use continuous radiation. An example of a thermal processing apparatus using a continuous radiation source in the form of a laser diode is filed on March 27, 2000 and assigned to the same assignee as the present application “having a radiant energy radiation source for exposing a substrate. US patent application Ser. No. 09 / 536,869 entitled “Apparatus having Line Source of Radiant Energy for Exposing a Substrate”. With a laser diode bar array, an output power in the range of 100 W / cm can be obtained and an image can be formed to form a line image with a width of about 1 micron. Also, the conversion from electricity to radiation is very efficient. Furthermore, since there are many diodes in the bar, each operating at a slightly different wavelength, it can be imaged to form a uniform line image.

  However, the use of a diode as a continuous radiation source is optimal only for certain applications. For example, when annealing a source / drain region having a depth of 1 micron or less, it is preferred that the radiation not be absorbed by silicon beyond that depth. However, the absorption length for a typical laser diode operating at a wavelength of 0.8 microns is about 20 microns for room temperature silicon. Thus, in thermal processing applications to process the top region of the substrate (eg, less than 1 micron), most of the radiation from the diode is much deeper than the required (or desired) depth. It penetrates inside. This increases the total power required. A thin absorbent coating can be used to alleviate this problem, but it adds complexity to an already quite complex manufacturing process.

[Summary of Invention]
The first aspect of the present invention is an apparatus for heat-treating a region of a substrate. The apparatus includes a continuous radiation source capable of providing a continuous radiation beam, the continuous radiation beam having a first intensity profile and wavelength capable of heating an area of the substrate. An optional system is disposed downstream of the continuous radiation source and is configured to receive the radiation beam and form a second radiation beam. The second radiation beam forms an image on the substrate. In an example embodiment, the image is a line image. The apparatus also includes a stage configured to support the substrate. At least one of the optical system and the stage scans the image in a scanning direction with respect to the substrate and uses a radiation pulse to heat the region to a temperature sufficient to process the region. Composed.

  Another aspect of the present invention is a method for heat treating a region of a substrate. The method includes generating a continuous beam of radiation having a wavelength capable of heating the region of the substrate, and then each point in the region receives an amount of thermal energy that can process the region of the substrate. Scanning the radiation in a scanning direction above the region.

  The various elements shown in the drawings are merely embodied and are not necessarily limited to scale. The proportions of certain elements are exaggerated, while others are minimized. The drawings are intended to illustrate various embodiments of the invention and can be understood and appropriately implemented by those skilled in the art.

Detailed Description of the Invention
In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and other embodiments may be utilized and may be modified without departing from the scope of the invention. It should be understood that it can be done. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

[Overview of apparatus and method]
FIG. 1A is a schematic diagram of a general embodiment of a laser scanning device of the present invention. The apparatus 10 of FIG. 1A includes a continuous radiation source 12 that emits a continuous radiation beam 14A along an optical axis A1, which is a measured output power and intensity profile P1 measured at an angle perpendicular to the optical axis. Have In an example embodiment, the radiation beam 14A is collimated. Further, in one example embodiment, the radiation source 12 is a laser and the radiation beam 14A is a laser beam. In one embodiment, radiation source 12 is a carbon dioxide (CO ₂ ) laser operating at a wavelength between about 9.4 microns and about 10.8 microns. Since the CO ₂ laser converts electricity to radiation very efficiently and the output beam is usually very coherent, the profile P1 is Gaussian. Further, as will be described later, the infrared wavelength generated by the CO ₂ laser is suitable for processing (eg, heating) silicon (eg, a silicon substrate such as a semiconductor wafer). Also, in one embodiment, the radiation beam 14A is linearly polarized and can be manipulated such that the radiation incident on the substrate includes only the p-polarization state P, only the s-polarization state S, or both. Since the radiation source 12 emits a continuous radiation beam 14A, it is referred to herein as a “continuous radiation source”. Typically, the radiation beam 14A includes radiation of a wavelength that can be absorbed by the substrate and thereby heat the substrate.

  The apparatus 10 also includes an optical system 20 downstream of the radiation source 12 that changes (eg, focuses or shapes) the radiation beam 14A to form the radiation beam 14B. The optical system 20 may consist of a single element (for example, a lens member or a mirror) or may be manufactured from a plurality of members. In one embodiment, the optical system 20 can also include a movable member, such as a scanning mirror, as described in detail below.

  The apparatus 10 further includes a chuck 40 having an upper surface 42 downstream of the optical system 20. The chuck 40 is supported by a stage 46, and the stage 46 is supported by a platen 50. In an example embodiment, the chuck 40 is incorporated into the stage 46. In another example of embodiment, the stage 46 is movable. In an example embodiment, the substrate stage 46 can rotate about about one or more of the x, y, and z axes. The upper surface 42 of the chuck can support the substrate 60, which has a surface 62 having a surface normal N and an edge 63.

  In one example embodiment, as described below, the substrate 60 includes a reference shape 64 that facilitates alignment of the substrate within the apparatus 10. In one example embodiment, the reference shape 64 also functions to identify the crystal orientation of the single crystal substrate 60. In one example embodiment, the substrate 60 is a #Semi M1-600 “polished single crystal silicon wafer available from the International Semiconductor Manufacturing Equipment Association (SEMI) of San Jose City, 95134 Zanker Road, 3081. A single crystal silicon wafer as described in “Specifications”, which is incorporated herein by reference.

  In one example of the embodiment, the substrate 60 includes source and drain regions 66A and 66B formed on or near the surface 62 as part of a circuit (eg, transistor) 67 formed in the substrate. In an example embodiment, the source and drain regions 66A, 66B are shallow and have a depth of 1 micron or less toward the interior of the substrate.

  The axis A1 and the substrate normal N form an angle Φ, which is the incident angle Φ that the radiation beam 14B (and the axis A1) makes with the normal N of the substrate surface. In one example embodiment, the radiation beam 14B has an angle of incidence Φ> 0, which prevents radiation reflected from the substrate surface 62 from returning to the radiation source 12. Usually, the incident angle can be varied in the range of 0 ° ≦ φ <90 °. However, as will be described in more detail below, in certain applications it is beneficial to operate the device at a selected angle of incidence within this range.

  In one example embodiment, the apparatus 10 further includes a controller 70 that is connected to the radiation source 12 via a communication line (“line”) 72 and is connected to the stage controller 76 via a line 78. . The stage controller 76 is operatively connected to the stage 46 via a line 80 and controls the movement of the stage. In an example embodiment, the controller 70 is connected to the optical system 20 via a line 82. The controller 70 controls operations of the radiation source 12, the stage controller 76, and the optical system 20 (for example, movement of internal members) via the signals 90, 92, and 94.

  In one example embodiment, one or more lines 72, 78, 80, and 82 are wires, and the corresponding one or more signals 90, 92, and 94 are electrical signals, and in another example embodiment, one or more lines. The lines are optical fibers, and the corresponding one or more of the signals are optical signals.

  In one example embodiment, controller 70 is a computer, such as a personal computer or workstation, and is available from a number of well-known computer companies, such as Dell Computer Corporation of Austin, Texas. Preferably, the controller 70 is suitable for connecting the processor to a storage device such as a hard disk drive and any of a number of commercially available microprocessors such as the Intel PENTIUM® series or AMD K6 or K7 processors. Bus architecture and appropriate input / output devices (eg, keyboard and display, respectively).

  With continued reference to FIG. 1A, the radiation beam 14B is directed by the optical system 20 onto the surface 62 of the substrate along axis A1. In one example embodiment, the optical system 20 focuses the radiation beam 14B to form the image 100 on the surface 62 of the substrate. In this specification, the term “image” is typically used to describe the distribution of light formed on the surface 62 of the substrate by the radiation beam 14B. Thus, the image 100 need not necessarily have an associated object in the conventional sense. Further, the image 100 does not necessarily have to be formed by focusing light rays. For example, the image 100 can be an elliptical spot formed by the anamorphic optical system 20, and a circular spot formed by a normal incident focused beam formed from a circularly symmetric optical system. Also good. Also, the term “image” includes the distribution of light formed on the surface 62 of the substrate by blocking the beam 14 B with the substrate 60.

  The image 100 can have any number of shapes, such as a square, a rectangle, and an ellipse. The image 100 can also have a variety of different intensity distributions, including those corresponding to a uniform line image distribution. FIG. 1B shows an example of an embodiment of an image 100 as a line image. The idealized line image 100 has a long dimension (length) L1, a short dimension (width) L2, and a uniform (that is, flat-top, flat top) intensity. In practice, the line image 100 is not completely uniform due to diffraction effects.

  FIG. 1C is a two-dimensional plot showing the intensity distribution for an actual line image. For most applications, the integrated cross-sectional area at the short dimension L2 need only be substantially uniform at the long dimension L1, and the uniformity of the integrated intensity distribution in the operatively useful part of the image is about ± 2. %.

With continued reference to FIGS. 1B and 1C, in one example embodiment, the length L1 ranges from about 1.25 cm to 4.4 cm and the width L2 is about 50 microns. In another example of the embodiment, the length L1 is 1 cm or less. Furthermore, in an example embodiment, the image 100 has an intensity in the range of 50 kW / cm ² to 150 kW / cm ² . The intensity of the image 100 is selected based on the amount of energy that needs to be imparted to the substrate for a particular application, the image width L2, and the speed at which the image is scanned over the surface 62 of the substrate.

  FIG. 1D is a schematic diagram of an optical system 20 including conical mirrors M1, M2, and M3 that form a line image on the surface of the substrate. The optical system 20 of FIG. 1D shows how a reflective cone segment can be used to focus a collimated beam into the line image 100. In one example embodiment, the optical system 20 includes columnar parabolic mirror segments M1, M2 and a conical mirror segment M3. The conical mirror segment M3 has an axis A3 associated with the entire conical mirror (indicated by a phantom). The axis A3 is parallel to the parallel beam 14A and is located along the surface 62 of the substrate.

  The line image 100 is formed on the surface 62 of the substrate along the axis A3. The advantage of this arrangement of the optical system 20 is that a narrow diffraction limited image 100 is formed with minimal variation in the incident angle Φ. The length L1 of the line image mainly depends on the incident angle Φ and the size of the parallel beam measured in the y-direction. Different angles of incidence Φ can be achieved by switching different conical mirror segments (eg, mirror M3 ') to the path of the radiation beam 14A'. The length L1 of the line image 100 can be changed by changing the collimated beam size using, for example, an adjustable (eg, zoom) collimating optical system 104.

  With continued reference to FIG. 1D, in one example embodiment, the size of the collimated beam 14A 'can be changed using columnar parabolic mirrors M1, M2. The collimated beam 14A 'is first line focused at point F by a positive parabolic mirror M1. Prior to focusing at point F, the focused beam 14A 'is interrupted by a negative parabolic mirror M2, which collimates the focused beam. The two columnar parabolic mirrors M1, M2 change the width of the parallel beam only in the y-direction. Accordingly, the parabolic mirrors M1, M2 also change the length L1 of the line image 100 at the substrate surface 62, but do not change the line image width L2 in the direction perpendicular to the plane of the drawing.

  Also shown in FIG. 1D are alternative paraboloidal mirrors M1 ′, M2 ′ and alternative conical mirrors M3 ′, which use, for example, index wheels 106, 108, and 110 in the optical path. It can be arranged at a predetermined fixed position.

  Referring again to FIG. 1A, in one example embodiment, the surface 62 of the substrate is scanned under the image 100 using one of many scanning patterns, as will be described in more detail below. Scanning can be accomplished in many ways, including moving either the substrate stage 46 or the radiation beam 14B. Thus, as used herein, the term “scan” includes image movement relative to the surface of the substrate, regardless of how it is accomplished.

By scanning a continuous radiation beam over the surface 62 of the substrate, for example, one or more selected regions such as regions 66A, 66B, or one or more circuits such as transistors 67, each irradiation point on the substrate is exposed to a radiation pulse. Receive. In an example embodiment employing a 200 microsecond dwell time (i.e., the time that the image exists above a given point), the amount of energy received by each scan point on the substrate during each scan is between 5 J / cm ² and 50 J. / Cm ² range. Overlapping scans further increase the total absorbed energy. Thus, in apparatus 10, a continuous radiation source rather than a pulsed radiation source is used for controlled pulse or burst radiation to each point on the substrate with one or more regions, eg, circuits or circuit elements formed in or on top. It can be used to give enough energy to process. As used herein, the term “treatment” includes selective melting, explosive recrystallization, and dopant activation.

  Also, as used herein, the term “processing” does not include laser ablation, laser cleaning of the substrate, or photolithography exposure, and subsequent chemical activation of the photoresist. Rather, for example, the image 100 may be used to increase the surface temperature of one or more regions to process one or more regions (eg, to activate the dopants in the source and drain regions 66A, 66B, or the one or more regions). The substrate 60 is scanned to provide sufficient thermal energy (to change the crystalline structure of the region). In one example of a heat treatment embodiment, the apparatus 10 heats and heats shallow source / drain regions (ie, source and drain regions 66A, 66B, etc. of a transistor 67 having a depth of 1 micron or less from the surface 62 inside the substrate). Used to cool and thereby activate.

  As illustrated by the examples described below, the device 10 has many different embodiments.

[Embodiment having a beam converter]
In the embodiment shown in FIG. 1A, the profile P1 of the radiation beam 14A is non-uniform. Such a situation may occur, for example, when the radiation source 12 is a substantially coherent laser and the final energy distribution in the parallel beam is Gaussian, so that the parallel beam is a substrate. A similar energy distribution is generated when an image is formed on the. Depending on the application, the radiation beams 14A, 14B have a more uniform distribution and the size of the radiation beams 14A, 14B so that the image 100 has an appropriate intensity distribution and size for heat treating the substrate in a given application. It may be desirable to change the height.

  FIG. 2A is a schematic diagram showing an example of an embodiment of the laser scanning device 10 of FIG. 1A, and this laser scanning device 10 is disposed along the axis A <b> 1 between the optical system 20 and the continuous radiation source 12. A beam converter 150 is further included. The beam converter 150 converts the radiation beam 14A having the intensity profile P1 into the deformed radiation beam 14A 'having the intensity profile P2. In one example embodiment, beam converter 150 and optical system 20 are combined to form a single converter / optical system 160. Although the beam converter 150 is arranged upstream of the optical system 20, it can be arranged downstream of the optical system 20.

  FIG. 2B is a schematic diagram showing how the beam converter 150 converts the radiation beam 14A having the intensity profile P1 into the deformed radiation beam 14A ′ having the intensity profile P2. The radiation beams 14A, 14A 'are shown to be composed of light rays 170, with the light beam spacing corresponding to the relative intensity distribution of the radiation beams. The beam converter 150 adjusts the relative spacing (ie, density) of the rays 170 to change the profile P1 of the radiation beam 14A to form a deformed radiation beam 14A 'having a profile P2. In one example embodiment, the beam converter 150 is a dioptric, catoptric or catadioptric lens system.

  FIG. 2C is a cross-sectional view of an example of an embodiment of the converter / optical system 160, and the converter / optical system 160 includes a converter 150 and an optical system 20. The converter 150 converts the radiation beam 14A having a Gaussian profile P1 into a radiation beam 14A 'having a flat top (ie, uniform) profile P2. The optical system 20 forms a focused radiation beam 14B and a line image 100. The converter / focusing system 160 of FIG. 2C includes cylindrical lenses L1-L5. Here, “lens” may mean an individual lens member or a group of lens members (ie, a lens group). The first two cylindrical lenses L1 and L2 reduce the diameter of the radiation beam 14A, while the cylindrical lenses L3 and L4 enlarge the radiation beam 14A to its original size, but due to the spherical aberration of the lens. The resulting deformed radiation beam profile 14A '. Since the fifth cylindrical lens L5 functions as the optical system 20 and is rotated 90 ° relative to the other lenses, the magnification is deviated from the plane of the drawing. The lens L5 forms a radiation beam 14B, and the radiation beam 14B forms a line image 100 on the substrate 60.

  In one example embodiment, the converter / focusing system 160 of FIG. 2C also includes a vignette aperture 180 disposed upstream of the lens L1. Vignette aperture 180 removes the outermost rays of input beam 14A, which are overcorrected by spherical aberrations in the system, while resulting in intensity bumps at the edges of the flat intensity profile.

  FIG. 2D is an example plot of an intensity profile P2 of a non-vignetted uniform radiation beam 14A 'as formed by a typical beam converter 150. Typically, the flat top radiation beam profile P2 has a flat portion 200 in most of its length and includes an intensity peak 210 in the vicinity of the beam end 204. By removing the rays outside the beam using the vignette aperture 180, it is also possible to obtain a more uniform radiation beam profile P2 as shown in FIG. 2E.

  By vignetting the outermost rays of the radiation beam 14A, an increase in intensity at the beam end 204 can be prevented, but a certain increase in intensity in the vicinity of the beam end causes uniform heating. desirable. Heat is lost at the beam end 204 in a direction parallel to and perpendicular to the line image 100 (FIG. 1B). Therefore, the higher the intensity at the beam end 204, the higher the heat loss arrow can be compensated. Thus, a more uniform temperature distribution on the substrate is obtained when the image 100 is scanned over the substrate 60.

[Further embodiment]
FIG. 3 is a schematic view of an apparatus 10 similar to the apparatus of FIG. 1A, which further includes a number of additional members disposed above the substrate 60 at the top of the figure. These additional members are included alone or in various combinations to illustrate additional embodiments of the present invention. The operations performed by the following example embodiments require some of the additional members introduced in FIG. 3 and whether the members described in the above-described embodiments are also required in the described embodiments. Will be apparent to those skilled in the art. For ease of explanation, since some of these embodiments are based on the previously described embodiments, FIG. 3 includes all of the components required for these additional embodiments. As shown. Examples of these additional embodiments are described below.

[Attenuator]
Referring to FIG. 3, in one example embodiment, the apparatus 10 includes an attenuator 226 disposed downstream of the radiation source 12, and selects the radiation beam 14A, beam 14A ′, or beam 14B depending on the position of the attenuator. Attenuate. In one embodiment, the radiation beam 14A is polarized in a particular direction (eg, p, s or a combination thereof), the attenuator 226 includes a polarizer 227, and the polarizer 227 is relative to the polarization direction of the radiation beam. , Which attenuates the beam. In another embodiment, the attenuator 226 includes at least one of a removable attenuation filter or a programmable attenuation wheel that includes a plurality of attenuator members.

  In one example embodiment, attenuator 226 is connected to controller 70 via line 228 and is controlled by signal 229 from the controller.

[¼ wave plate]
In another example embodiment, the radiation beam 14A is linearly polarized and the apparatus 10 includes a quarter wave plate 230 downstream of the radiation source 12 for converting the linearly polarized light into circularly polarized light. In an example embodiment where the attenuator includes a polarizer 227 to prevent radiation reflected or scattered from the substrate 62 from returning to the radiation source 12, the quarter wave plate 230 operates in conjunction with the attenuator 226. To do. In particular, in the return path, the reflected circularly polarized radiation is converted to linearly polarized radiation and blocked by the polarizer 227. This configuration is particularly useful when the incident angle Φ is 0 or in the vicinity of 0 (ie, normal incidence or almost normal incidence).

[Beam energy monitoring system]
In another example embodiment, the apparatus 10 includes a beam energy monitoring system 250 disposed downstream of the radiation source 12 along the axis A1 and monitoring the energy of each beam. System 250 is connected to controller 70 via line 252 and provides a signal 254 indicative of each measured beam energy to the controller.

[Fold mirror]
In another example embodiment, the device 10 includes a fold mirror 260 that makes the device more compact or forms a particular device geometry. In one example embodiment, the fold mirror 260 is movable and adjusts the direction of the beam 14A ′.

  In an example embodiment, the fold mirror 260 is connected to the controller 70 via a line 262 and is controlled by a signal 264 from the controller.

[Reflected radiation monitor]
With continued reference to FIG. 3, in another example embodiment, the apparatus 10 includes a reflected radiation monitor 280 positioned to receive radiation 281 reflected by the surface 62 of the substrate. Monitor 280 is connected to controller 70 via line 282 and provides a signal 284 indicating the amount of reflected radiation 281 measured to the controller.

  FIG. 4 shows an example of an embodiment of a reflected radiation monitor 280 for an example of an embodiment of the apparatus 10 where the incident angle Φ (FIGS. 1 and 2A) is 0 ° or near 0 °. Reflected radiation monitor 280 utilizes beam splitter 285 along axis A1 to direct a small portion of reflected radiation 281 (FIG. 3) to detector 287. The monitor 280 is connected to the controller 70 via a line 282 and supplies a signal 284 indicating each detected radiation to the controller. In one example embodiment, a focusing lens 290 is included to focus the reflected radiation 281 on the detector 287.

  The reflected radiation monitor 280 has multiple uses. In one mode of operation, the image 100 is made as small as possible and changes in the reflected radiation monitoring signal 284 are measured. This information is then used to evaluate the reflectance variation on the substrate. This mode of operation requires that the response time of the detector (eg, detector 287) be equal to less than the dwell time of the scanning beam. The variation in reflectivity is minimized by adjusting the incident angle Φ, adjusting the polarization direction of the incident beam 14B, or both.

  In the second mode of operation, the beam energy monitoring signal 254 (FIG. 3) from the beam energy monitoring system 250 and the radiation monitoring signal 284 are combined to achieve an accurate measurement of the amount of absorbed radiation. Next, the energy of the radiation beam 14B is adjusted to maintain the absorbed radiation at a constant level. This modification of the operation mode includes adjusting the scanning speed in a manner corresponding to absorbed radiation.

  In the third mode of operation, the reflected radiation monitoring signal 284 is compared to a threshold value and the signal that exceeds the threshold value is used as a warning that an unexpected anomaly has occurred that requires further investigation. In one example embodiment, the data regarding the variation in reflected radiation is archived with the corresponding substrate identification code (eg, stored in the memory of the controller 70) to determine the root cause of the anomaly found after processing the substrate. To help you.

[Diagnostic system]
In many heat treatments, it is beneficial to know the maximum temperature or temperature-time profile of the surface being treated. For example, in the case of junction annealing, it is desirable to control the maximum temperature reached during LTP very closely. Tight control is achieved by using the measured temperature to control the output power of the continuous radiation source. Ideally, such a control system has a response capability equal to or faster than the dwell time of the scanned image.

  Thus, referring again to FIG. 3, in another example embodiment, the apparatus 10 includes a diagnostic system 300 that communicates with the substrate 60. The diagnostic system 300 is connected to the controller 70 via a line 302 and is configured to perform a predetermined diagnostic operation such as measurement of the temperature of the substrate 62. The diagnostic system 300 provides a signal 304 indicating each diagnostic measurement such as the substrate temperature to the controller.

  Referring back to FIG. 4, when the incident angle Φ is 0 ° or in the vicinity of 0 °, the diagnostic system 300 is rotated so as to deviate from the path of the focusing optical system 20.

  FIG. 5 is an enlarged view of an example embodiment of a diagnostic system 300 that is used to measure the temperature at or near the position of the scanned image 100. The system 300 of FIG. 5 separates the collected radiation 310 along the axis A2 and the collected radiation 310 and connects to the controller 70 via lines 302A and 302B, respectively. And a beam splitter 346 for directing radiation toward the two detectors 350A and 350B. Detectors 350A and 350B detect different spectral bands of radiation 310.

  A very simple configuration of the diagnostic system 300 includes a single detector, such as a silicon detector 350A, for observing the hottest spot at the falling edge of the radiation beam (FIG. 3). Typically, the various films (not shown) on the substrate that the image 100 encounters will have different reflectivity, so the signal 304 from such a detector will vary. For example, silicon, silicon oxide, and polysilicon films above the oxide layer all have different reflectivities at normal incidence and thus have different thermal emissivities.

  One way to deal with this problem is to estimate the temperature using only the highest signal available in a given period. This approach improves accuracy at the expense of reduced detector response time.

  With continued reference to FIG. 5, in one example embodiment, the collection optics 340 is focused on the falling edge of the image 100 (moving in the direction indicated by arrow 354) from the hottest point on the substrate 60. The emitted radiation 310 is collected. Accordingly, the hottest (ie, highest) temperature on the substrate 60 can be monitored and controlled directly. Control of the substrate temperature can be accomplished in a number of ways, including changing the power of the continuous radiation source 12, adjusting the attenuator 226 (FIG. 3), changing the substrate scan speed or image scan speed, or combinations thereof. Can be achieved.

  The temperature of the substrate 60 can be measured by monitoring the generated radiation 310 of a single wavelength, provided that the entire surface 62 has the same emissivity. If the surface 62 is patterned, the temperature can be measured by monitoring the ratio between two closely spaced wavelengths during a scanning operation, assuming that the emissivity does not change rapidly with wavelength.

  FIG. 6 is a black body temperature profile (plot) of intensity versus wavelength at a temperature of 1410 ° C., which is the source and drain region of a semiconductor transistor, ie, the source and drain region 66A of transistor 67 (FIG. 3). , 66B, the upper limit used for a given heat treatment application to activate the dopant. As is apparent from FIG. 6, temperatures around 1410 ° C. are monitored at 0.8 microns and 1.0 microns using detectors 350A, 350B in the form of silicon detector arrays. Compared to a single detector, the advantage of using a detector array is that many temperature samples are obtained on the image 100 along the image 100 to quickly eliminate any temperature non-uniformities or irregularities. Is that you can find in In an example embodiment that includes dopant activation of the source and drain regions 66A, 66B, the temperature needs to be raised to 1400 ° C. with a maximum temperature variation between two points of less than 10 ° C.

  For temperature control in the region of 1400 ° C., the two spectral regions can be 500-800 nm and 800-1100 nm. Assuming that the ratio of emissivity in the two spectral regions does not vary with different materials on the surface of the substrate, the ratio of the signals from the two detectors can be precisely related to temperature. By using the ratio of the signals 304A, 304B from the silicon detectors 350A, 350B for temperature adjustment, a control loop bandwidth having a response time approximately equal to the dwell time can be achieved relatively easily.

  Another approach is to use detectors 350A, 350B in the form of a detector array, where both arrays image the same area of the substrate, but use different spectral regions. With this arrangement, a temperature profile of the treated area is obtained and both maximum temperature and temperature uniformity can be accurately evaluated. This arrangement can also adjust the uniformity of the intensity profile. By using a silicon detector in such an arrangement, a control loop bandwidth with a response time approximately equal to the dwell time is possible.

  Another way to compensate for variations in the emissivity of the film present on the substrate is to make the diagnostic system 300 face the substrate surface 62 at an angle near the Brewster angle of silicon using p-polarized radiation. Is to place. In this case, the Brewster angle is calculated at a wavelength corresponding to the wavelength detected by the diagnostic system 300. Since the extinction coefficient is very consistent with the Brewster angle, so is the emissivity. In one embodiment, this method is combined with a method that uses two detector arrays to obtain the ratio of signals at two adjacent wavelengths. In this case, as shown in FIG. 7, the plane containing the viewing axis of the diagnostic system 300 may be perpendicular to the plane 440 containing the radiation beam 14B and the reflected radiation 281.

  The scanned image 100 can cause uniform heating over a large portion of the substrate. However, along with many defects that can occur in optical columns, diffraction can interfere with image formation and cause unexpected results such as non-uniform heating. It is therefore highly desirable to have a built-in image monitoring system that can directly measure the uniformity of energy in the image.

  FIG. 5 shows an example of an embodiment of the image monitoring system 360. In one example embodiment, the image monitoring system 360 is located in the scan path and in a plane PS defined by the substrate surface 62. The image monitoring system 360 includes a pinhole 362 facing the scan path and a detector 364 behind the pinhole. In operation, the substrate stage 46 is positioned so that the detector 364 samples the image 100 showing points on the substrate that would be seen during a typical scan of the image. Image monitoring system 360 is connected to controller 70 via line 366 and provides a signal 368 indicative of the detected radiation to the controller.

  By sampling a portion of the image, the data necessary to determine the image intensity profile (eg, FIG. 1C) is obtained, and thereby the heating uniformity of the substrate can be measured.

[Substrate pre-aligner]
Referring again to FIG. 3, in some cases, the substrate 60 needs to be placed on the chuck 40 in a predefined orientation. For example, the substrate 60 can be crystalline (eg, a crystalline silicon wafer). In heat treatment applications using crystalline substrates, the inventors often prefer that the crystal axis be aligned in a selected direction with respect to the image 100 in order to optimize processing. I found it.

Thus, in one example embodiment, the apparatus 10 includes a pre-aligner 376 connected to the controller 70 via line 378. The pre-aligner 376 receives the substrate 60, positions the reference shape 64, such as flat or notched, and moves (eg, rotates) the substrate 60 until the reference shape is aligned in the selected direction. aligned with the reference position P _R, to optimize the process. Once the substrate is aligned, signal 380 is sent to controller 70. Next, the substrate is fed from the pre-aligner 40 to the chuck 40 via the substrate handler 386. The substrate handler 386 is operatively connected to the chuck and pre-aligner 376. Substrate handler 386 is connected to controller 70 via line 338 and is controlled by signal 390. The substrate 60 is then placed on the chuck 40 in a selected orientation that corresponds to the orientation of the substrate pre-aligned on the pre-aligner 376.

[Measurement of absorbed radiation]
By the substrate 60 by measuring the energy of one of the radiation beams 14A, 14A ′, or 14B using the beam energy monitoring system 250 and measuring the energy of the reflected radiation 281 using the monitoring system 280. The absorbed radiation can be determined. Thereby, the radiation absorbed by the substrate 60 can be kept constant during scanning regardless of the change in the reflectance of the surface 62 of the substrate. In one example embodiment, maintaining constant energy absorption per unit area is one of the output energy of the continuous radiation source 12, the scanning speed of the image 100 over the surface 62 of the substrate, and the attenuation of the attenuator 226. This is achieved by adjusting the above.

  In one example embodiment, constant energy absorption per unit area is achieved by changing the polarization of the radiation beam 14B (eg, rotating the quarter wave plate 230). In another example of the embodiment, the energy absorbed per unit area is changed or maintained by a combination of the above-described methods. Absorption in selected infrared wavelengths of silicon is greatly increased by dopant impurities that improve the conductivity of the silicon. Even if the minimum absorption of incident radiation is achieved at room temperature, the absorption increases with increasing temperature, resulting in a steep rise cycle in which all incident energy is absorbed only by a surface layer that is a few microns deep.

  Thus, the heating depth in a silicon wafer is determined primarily by the diffusion of heat from the surface of the silicon, rather than by the absorption depth of infrared wavelengths at room temperature. Also, doping with silicon having n-type or p-type impurities increases absorption at room temperature, further promoting a steep rising cycle leading from material surface to strong absorption at a few microns.

[Brewster angle or incident angle near it]
In one example of the embodiment, the incident angle Φ is set to correspond to the Brewster angle. At the Brewster angle, all the p-polarized radiation P (FIG. 3) is absorbed by the substrate 60. The Brewster angle depends on the refractive index of the material on which the radiation is incident. For example, the Brewster angle is 73.69 ° in the case of room temperature silicon and a wavelength λ of 10.6 microns. Since about 30% of the incident radiation beam 14B is reflected at normal incidence (Φ = 0), the unit area required to perform the heat treatment by using p-polarized radiation at or near the Brewster angle. The power per hit can be greatly reduced. Also, by using a relatively large incident angle Φ such as a Brewster angle, the width of the image 100 in one direction can be expanded to cos ⁻¹ φ times or about 3.5 times the normal incident image width. it can. The effective depth of focus of image 100 also decreases at a similar magnification.

  If the substrate 60 has a surface 62 having a variety of different regions, including those having multiple layers, typically as in semiconductor processing to form an IC, the optimum angle for processing is Can be determined by plotting the reflectivity versus the incident angle Φ in various regions. Usually, for p-polarized radiation, the minimum reflectance occurs near the Brewster angle of the substrate. Typically, an angle or a small range of angles can be found that minimizes and equalizes the reflectivity of each region.

  In an example embodiment, the incident angle Φ is limited to an angular range around the Brewster angle. For example, in the above example where the Brewster angle is 73.69 °, the incident angle Φ is limited to between 65 ° and 80 °.

[Optimization of radiation beam geometry]
In one example embodiment, a very small portion of material at the surface of the substrate is heated to near the melting point of the substrate by scanning the image 100 over the surface 62 and heat treating the substrate 60. Therefore, a considerable amount of stress and strain is generated in the heated part of the substrate. In some situations, undesired sliding surfaces that propagate to surface 62 due to stress occur.

  In one example embodiment, the radiation beam 14A is polarized. In such a case, it is practical to select the direction of the polarization direction of the radiation beam 14B relative to the surface 62 of the substrate as well as the direction of the radiation beam 14B incident on the surface 62, thereby obtaining the most efficient processing. It is done. Further, the heat treatment of the substrate 60 is often performed after many other processes that change the properties (eg, structure and topography) of the substrate.

  FIG. 7 is an enlarged isometric view of an example of a substrate 60 in the form of a semiconductor wafer having a pattern 400 formed thereon. In one example embodiment, the pattern 400 includes lines or edges 404, 406 that conform to a grid (ie, Manhattan geometry) that extend in the X-direction and the Y-direction. Lines / edges 404, 406 correspond to, for example, polyrunner, gate, and field oxide isolation region edges or IC chip boundaries. Generally, in the manufacture of IC chips, the substrate is patterned in a shape that extends mostly at right angles to each other.

  Therefore, for example, in the process of forming an IC chip, the surface 62 becomes extremely complicated when the substrate (wafer) 60 reaches a stage where annealing or activation of the source and drain regions 66A and 66B is required. For example, in a typical IC manufacturing process, one region of the surface 62 may be bare silicon and another region of the surface may have a relatively thick silicon oxide isolation trench. This region may have a thin polysilicon conductor across the thick oxide trench.

  Thus, if care is not taken, the line image 100 may be reflected or diffracted in some parts of the surface 62 of the substrate and selectively in other parts, depending on the surface structure including the main direction of the lines / edges 404, 406. Can be absorbed. This is especially true for embodiments that polarize the radiation beam 14B. As a result, non-uniform substrate heating generally occurs during heat treatment.

  Thus, with continued reference to FIG. 7, in one example embodiment of the present invention, the optimal radiation beam geometry that minimizes the variation in absorption of the radiation beam 14B in the substrate 60, ie, polarization direction, incident angle Φ, scan direction It is desirable to find the scanning speed and the image angle θ. Furthermore, it is desirable to find a radiation beam geometry that minimizes the formation of sliding surfaces on the substrate.

  The point-to-point variation of the radiation 281 reflected from the substrate 60 is caused by a number of factors including variations in film composition, the number and proportion of lines / edges 404, 406, the orientation of the polarization direction, and the incident angle Φ.

  With continued reference to FIG. 7, the plane 440 is defined as the plane containing the radiation beam 14B and the reflected radiation 281. By irradiating the substrate with the radiation beam 14B so that the plane 440 intersects the surface 62 of the substrate at 45 ° with respect to the lines / edges 404, 406, reflection variations due to the presence of the lines / edges 404, 406 are minimized. can do. The line image is formed such that the length direction is aligned with the plane 440 or is perpendicular to the plane. Therefore, regardless of the incident angle Φ, the image angle θ between the line image 100 and each line / edge 404, 406 is 45 °.

  Variations in the amount of reflected radiation 281 due to various structures (eg, lines / edges 404, 406) on the surface 62 of the substrate can be further reduced by appropriate selection of the incident angle Φ. For example, when forming a transistor as part of an IC, when the substrate 60 is ready to anneal or activate the source and drain regions 66A, 66B, the substrate typically performs all of the following topography. Would include: a) bare silicon, b) oxide isolation region embedded in silicon (eg, about 0.5 microns thick), c) thin over embedded oxide isolation region (eg, 0.1 Micron) Polysilicon runner.

  FIG. 8 shows the respective p-polarized P and s-polarized S of the above topography on an undoped silicon substrate in the case of laser radiation with a wavelength of 10.6 microns, with an infinitely deep silicon dioxide layer reflectivity. It is a plot of room temperature reflectance. From FIG. 8, it is very clear that the reflectivity varies greatly depending on the polarization and the incident angle Φ.

  For p-polarized light P (ie, polarization at plane 440) where the incident angle Φ is between about 65 ° and about 80 °, the reflectivity of all four cases is minimal and the variation between cases is also minimal. is there. Accordingly, the range of incident angles Φ between about 65 ° and about 80 ° is within the range of semiconductor substrates (eg, silicon substrates), since the required total power and the point-to-point variation in absorbed radiation is minimized. Is particularly suitable for the apparatus 10 for heat-treating the activated doped regions formed in

  Due to the presence of dopants or high temperatures, the silicon becomes more metallic and the minimum corresponding to the Brewster angle shifts to higher angles and higher reflectivity. Thus, for doped substrates and / or higher temperatures, the optimum angle will be higher than the corresponding Brewster angle of undoped material at room temperature.

  FIG. 9 is a plan isometric view of the apparatus 10 used to process the substrate 60 in the form of a semiconductor wafer, illustrating the operation of the apparatus in an optimal radiation beam geometry. The wafer 60 includes a lattice pattern 400 formed thereon, and each square 468 in the lattice represents, for example, an IC chip (such as the circuit 67 in FIG. 1A). The line image 100 is scanned with respect to the surface 62 of the substrate (wafer) in a direction 470 that results in an image angle θ of 45 °.

[Description of crystal orientation]
As described above, a crystalline substrate, such as a single crystal silicon wafer, has a crystal plane with an orientation often indicated by a reference shape 64 (eg, a notch or a flat shown in FIG. 9). The reference shape 64 is formed on the edge 63 corresponding to one direction of the main crystal plane in the substrate. Scanning the line image 100 can cause large thermal gradients and stress concentrations in the direction 474 perpendicular to the scanning direction 470 (FIG. 9), which can adversely affect the structural integrity of the crystalline substrate.

  With continued reference to FIG. 9, in the normal case, the silicon substrate 60 has a (100) crystal orientation and the lines / edges 404, 406 are relative to the two main crystal axes (100), (010) at the surface of the wafer. At 45 °. In order to minimize the formation of slip planes in the crystal, the preferred scanning direction is along one of the main crystal axes. Thus, the preferred scan direction to minimize slip formation in the crystal also coincides with the preferred direction for the silicon substrate lines / edges 404, 406 in the normal case. If a constant orientation is maintained between the line image 100, the line / edges 404, 406, and the crystal axes (100), (010), the scan of the line image relative to the substrate (wafer) 60 is circular or arcuate. Must be straight (for example, back and forth). Also, since a specific scanning direction is desirable with respect to the crystal orientation, in one example embodiment, the substrate is pre-aligned on the chuck 40 using, for example, a substrate pre-aligner 376 (FIG. 3).

  By carefully choosing the orientation between the substrate crystal axes (100), (010) and the scan direction 470, the possibility of slip planes being formed in the crystal lattice of the substrate by thermally induced stress. Can be minimized. It is believed that the optimal scanning direction in which the crystal lattice has the greatest resistance to slip induced by a sharp thermal gradient will depend on the nature of the crystal substrate. However, the optimal scan direction is tested by scanning the image 100 in a spiral pattern on a single crystal substrate and inspecting the wafer to determine the direction that can withstand the highest temperature gradient before showing slip. Can be found.

  For a substrate 60 in the form of a (100) crystalline silicon wafer, the optimum scanning direction is aligned at 45 ° with respect to the (100) substrate crystal lattice direction or the pattern lattice direction indicated by the lines / edges 404,406. . This has been confirmed experimentally by the inventors by scanning the radial line image 100 with a spiral pattern that gradually increases the maximum temperature as a function of distance from the center of the substrate. The optimum scanning direction was determined by comparing the direction showing the highest resistance to slip with the direction of the crystal axis.

[Image scanning]
(Bostrophedonic scanning)
FIG. 10 illustrates a cow pattern (ie, alternating back-and-forth or “X-Y”) scan pattern 520 of the image 100 over the surface 62 of the substrate that generates a short heat pulse at each point on the substrate that the image traverses. It is a top view of the board | substrate shown. Scan pattern 520 includes line scan segment 522. The cow plow scanning pattern 520 can be performed using a conventional bidirectional XY stage 46. However, such a stage usually has a considerable size and limited acceleration capability. If a very short dwell time (i.e., the time that the scanned image is on a given point on the substrate) is desired, the conventional stage takes considerable time to accelerate and decelerate. In addition, such a stage requires a large space. For example, for a dwell time of 10 microseconds with a beam width of 100 microns, a stage speed of 10 meters / second (m / second) is required. An acceleration of 1 g or 9.8 m / s ² requires 1.02 seconds and 5.1 m of travel for acceleration / deceleration. It is undesirable to provide 10.2 m of space on the stage for acceleration and deceleration.

(Optical scanning)
Scanning of image 100 on substrate surface 62 may be performed using a stationary substrate and a moving image, moving the substrate to keep the image stationary, or And by moving both the image and the image.

  FIG. 11 is a cross-sectional view of an example of an embodiment of the optical system 20 that includes the movable scanning mirror 260. By using optical scanning, a very efficient acceleration / deceleration speed (ie, the speed at which the stage will have to move to achieve the same scanning effect) can be achieved.

  In the optical system 20 of FIG. 11, the radiation beam 14A (or 14A ′) is reflected by the scanning mirror 260 positioned at the pupil of the f-θ relay optical system 20 including the cylindrical elements L10 to L13. In the example of the embodiment, the scanning mirror 260 is connected and driven to the servo motor unit 540, and the servo motor unit 540 is connected to the controller 70 via the line 542. Servo unit 540 is controlled by signal 544 from controller 70 via line 542.

  The optical system 20 scans the radiation beam 14B above the surface 62 of the substrate to form a moving image 100. Stage 46 increases the position of the substrate in the cross-scan direction after each scan to cover the desired area of the substrate.

In an exemplary embodiment, the lens element L10~L13 consists ZnSe, and infrared wavelengths of radiation emitted by CO ₂ lasers, transparent to both the near infrared and visible radiation emitted by the heated portion of the substrate It is. Thereby, the dichroic beam splitter 550 can be disposed in the path of the radiation beam 14A upstream of the scanning mirror 260, and the visible wavelength radiation and near infrared wavelength radiation emitted from the substrate are heated. The radiation beam 14A used to do so can be separated from the long wavelength radiation.

  The resulting radiation 310 is used to monitor and control the thermal processing of the substrate and is detected by the beam diagnostic system 560. The beam diagnostic system 560 includes a condenser lens 562 and a detector 564 connected to the controller 70 via a line 568. In one example embodiment, the resulting radiation 310 passes through a filter and is focused on a separate detector array 564 (only one is shown). A signal 570 corresponding to the radiation dose detected by detector 564 is provided to controller 70 via line 568.

  Although FIG. 11 shows a radiation beam 14B having an incident angle Φ = 0, in other embodiments, the incident angle is Φ> 0. In an example of the embodiment, the incident angle Φ is changed by appropriately rotating the substrate stage 46 about the axis AR.

  The advantage of optical scanning is that it can be performed very fast, so that minimal time is lost for beam or stage acceleration and deceleration. Using a commercially available scanning optical system, a stage acceleration equivalent to 8000 g can be achieved.

(Spiral scan)
In another embodiment, the image 100 is scanned in a spiral pattern relative to the substrate 60. FIG. 12 is a plan view of four substrates 60 positioned on the stage 46, and the stage can move relative to the image 100 in a rotational and linear manner to form a helical scan pattern 604. The rotational movement is performed about the rotation center 610. The stage 46 can support a plurality of substrates, and four substrates are shown in the figure for convenience of explanation.

  In one example embodiment, the stage 46 includes a linear stage 612 and a rotary stage 614. The spiral scan pattern 604 is formed by a combination of linear and rotational movement of the substrate so that each substrate is covered by a part of the spiral scan pattern. In order to keep the stay time constant at each point on the substrate, the rotation speed is changed in inverse proportion to the distance from the rotation center 610 to the image 100. The advantage of helical scanning is that there is no rapid acceleration / deceleration except at the beginning and end of the process. It is therefore practical to obtain a short residence time using such an arrangement. Another advantage is that multiple substrates can be processed in a single scanning operation.

(Alternate raster scanning)
When the image 100 is scanned over the substrate 60 with a cow plowing pattern with the spacing between adjacent path segments small, one segment is complete and the substrate is at the end of the scan segment where the next new segment begins. May be overheated. In such a case, the first part of the new scan path segment includes a significant thermal gradient due to the scan path segment immediately after completion. Unless the beam intensity is properly modified, this gradient will increase the temperature produced by the new scan. This makes it difficult to achieve a uniform maximum temperature across the entire substrate during scanning.

  FIGS. 13A and 13B are plan views of the substrate 60 showing an alternating raster scan path 700, which has line scan path segments 702 and 704. Referring to FIG. 13A, first, in the alternate raster scan path 700, the scan path segment 702 is scanned such that a gap 706 exists between adjacent scan paths. In one example embodiment, the gap 706 has a dimension equal to an integer multiple of the effective length of the line scan. In one example embodiment, the width of the gap 706 is the same as or approximately equal to the length L 1 of the image 100. Next, as shown in FIG. 13B, the scan path segment 704 is scanned to fill the gap. This scanning method greatly reduces the thermal gradient in the scan path that occurs with closely spaced scan path segments, making it easier to achieve a uniform maximum temperature across the substrate during scanning.

(Scanning pattern throughput comparison)
FIG. 14 shows simulated throughput (substrate / time) versus stay for the spiral scan method (curve 720), the optical scan method (curve 724), and the cattle plow (XY) scan method (curve 726). It is a plot of time (seconds). This comparison assumes an example of an embodiment using a 5 kW laser as a continuous radiation source used to form a Gaussian distributed beam, and therefore in an overlapping scan path using a 100 micron beam width L2. A scanned Gaussian image 100 is obtained with a radiation uniformity of about ± 2%.

  From this plot it can be seen that the helical scanning method has excellent efficiency under all conditions. However, since the helical scanning method processes multiple substrates at once, it requires a large surface that can support four chucks. For example, for four 300 mm wafers, the surface will be greater than about 800 mm in diameter. Another disadvantage of this method is that the distance between the scan line image and the crystal orientation of the substrate cannot be maintained in a constant direction, so that an optimal processing geometry cannot be maintained for a crystalline substrate.

  The optical scanning method is effective for an XY stage scanning system with a short residence time that has a throughput almost independent of the residence time and requires a high scanning speed.

  Many of the advantages and features of the present invention will be apparent from the detailed description, and therefore, the appended claims are intended to cover all of the advantages and features of the apparatus described above in accordance with the objects and scope of the present invention. Further, since many variations and modifications will readily occur to those skilled in the art, it is not desirable to limit the invention to the structure and operation itself described herein. Accordingly, other embodiments are within the scope of the appended claims.

FIG. 1A is a schematic diagram showing an apparatus of a general embodiment of the present invention. FIG. 1B shows an example of an ideal line image embodiment having a long dimension (length) L1 and a short dimension (width) L2 formed on a substrate by the apparatus of FIG. 1A. FIG. 1C is a two-dimensional plot showing the intensity distribution associated with the actual line image. FIG. 1D is a schematic diagram illustrating an example of an embodiment of an optical system for the apparatus of FIG. 1A that includes a conical mirror that forms a line image on the surface of the substrate. FIG. 2A is a schematic diagram illustrating an example of the embodiment of the laser scanning device of FIG. 1A, further including a beam converter disposed between the radiation source and the optical system. FIG. 2B is a schematic diagram illustrating how the beam converter of the apparatus of FIG. 2A changes the profile of the radiation beam. FIG. 2C is a cross-sectional view of an example of an embodiment of a converter / optical system including a Gaussian-to-flat top converter. FIG. 2D is a plot of an example of an intensity profile of a non-vignetted radiation beam formed, for example, by the converter / optical system of FIG. 2C. FIG. 2E is a plot similar to FIG. 2D that uses edge rays that are vignetted by the vignette aperture to reduce the intensity peak at the edges of the image. FIG. 3 is a schematic diagram showing an apparatus similar to the apparatus of FIG. 1A with additional elements, illustrating an example of a different embodiment of the present invention. FIG. 4 shows an example of an embodiment of the reflected radiation monitor of the apparatus of FIG. 3 when the incident angle Φ is 0 ° or near 0 °. FIG. 5 is an enlarged view of an example embodiment of the diagnostic system of the apparatus of FIG. 3 that is used to measure the temperature of the substrate at or near the position of the image during scanning. FIG. 6 is a relative intensity versus wavelength profile (plot) for a black body at 1410 ° C., which is slightly higher than the temperature used to activate the dopant in the source and drain regions of the semiconductor transistor. . FIG. 7 is an enlarged isometric view of a substrate having a shape aligned in the grating pattern, showing a 45 ° orientation of the plane containing the incident and reflected laser beams relative to the grating pattern shape. FIG. 8 is a plot of reflectance versus angle of incidence for p-polarized and s-polarized directions of a 10.6 micron wavelength laser radiation beam reflected from the following surfaces: (a) bare silicon, (b) silicon. 0.5 micron oxide isolation region on top of (c) 0.1 micron polysilicon runner on top of 0.5 micron oxide isolation region on silicon, and (d) infinitely deep oxidation Silicon layer. FIG. 9 is a plan isometric view of an apparatus of an embodiment of the present invention used to process a substrate, for example, in the form of a semiconductor wafer having a formed lattice pattern, with an optimal radiation beam geometry. The operation of the device is shown. FIG. 10 is a plan view of the substrate showing a cow pattern scan pattern of the image above the surface of the substrate. FIG. 11 is a cross-sectional view of an example of an embodiment of an optical system including a movable scanning mirror. FIG. 12 is a plan view of four substrates arranged on a stage that can be rotated and linearly moved to perform helical scanning of an image above the substrate. FIG. 13A is a plan view of a substrate showing an alternating raster scan pattern where the scan paths are separated by space so that the substrate can be cooled before scanning adjacent scan paths. FIG. 13B is a plan view of a substrate showing an alternating raster scan pattern where the scan paths are separated by space so that the substrate can be cooled before scanning adjacent scan paths. FIG. 14 is a simulated throughput (substrate / time) versus dwell time (microseconds) plot for a helical scan method, an optical scan method, and a cow tillage scan method for the apparatus of the present invention. is there.

Claims (76)

An apparatus for heat-treating a region of a substrate,
A continuous radiation source capable of providing a continuous first radiation beam;
An optical system configured to form a second radiation beam that receives the first radiation beam and forms an image on the substrate;
A stage configured to support the substrate;
Along the axis,
The first radiation beam has a first intensity profile and wavelength capable of heating a region of the substrate;
At least one of the optical system and the stage scans the image with respect to the substrate in a scanning direction and uses a radiation pulse to heat the region to a temperature at which heat treatment of the region is sufficient. Configured device. In claim 1,
The apparatus, wherein the image is a line image. In claim 1,
The optical system includes one or more curved mirrors. In claim 3,
The apparatus, wherein the one or more curved mirrors are conical mirrors. In claim 4,
A plurality of conical mirrors;
The apparatus wherein the plurality of conical mirrors each have a different cone angle and selective placement possibility and can be removed from the first radiation beam to form line images of different sizes. In claim 3,
The first radiation beam has a size;
The one or more curved mirrors include two or more sets of columnar parabolic mirrors with opposite outputs;
The apparatus wherein the columnar parabolic mirror is disposed in the first radiation beam to change the size and direction of the first radiation beam. In claim 6,
The apparatus wherein the set of columnar paraboloid mirrors has a selective placement possibility to change the size of the first radiation beam and is removable from the first radiation beam. In claim 1,
A beam converter disposed downstream of the radiation source,
The beam converter receives the first radiation beam and converts the first intensity profile into a second intensity profile. In claim 8,
The apparatus wherein the beam converter and the optical system are combined in a single converter / optical system. In claim 8,
The apparatus, wherein the first intensity profile is a Gaussian distribution. In claim 8,
The apparatus, wherein the second intensity profile is substantially uniform in a direction perpendicular to the scanning direction. In claim 1,
The apparatus wherein the continuous radiation source is a laser. In claim 1,
The apparatus, wherein the laser is a CO ₂ laser. In claim 13,
The apparatus wherein the wavelength is from about 9.4 μm to about 10.8 μm. In claim 1,
An apparatus comprising a stage controller coupled to the stage. In claim 15,
An apparatus comprising a controller coupled to at least one of the radiation source, the optical system, and the stage controller. In claim 1,
An adjustable attenuator disposed downstream of the radiation source;
A quarter-wave plate disposed downstream of the radiation source;
A fold mirror disposed downstream of the radiation source;
A pre-aligner that interlocks with the stage and receives the substrate and aligns the substrate with a reference position;
A monitor arranged adjacent to the stage and receiving and measuring radiation reflected from the substrate;
A diagnostic system disposed adjacent to the stage and receiving and measuring radiation emitted from the substrate;
A beam energy monitoring system disposed downstream of the radiation source and measuring the energy of one of the first and second radiation beams;
A device comprising one or more of the following. In claim 17,
The apparatus includes the fold mirror;
The apparatus, wherein the fold mirror is movable to scan the image above the substrate. In claim 17,
The apparatus includes the attenuator;
The apparatus wherein the attenuator includes an adjustable polarizer. In claim 17,
The apparatus includes the diagnostic system;
The diagnostic system includes first and second detectors;
The first and second detectors are configured to detect first and second spectral bands of the radiation emitted from the substrate, respectively, to determine a maximum temperature of the substrate; . In claim 1,
The apparatus includes: a scanning mirror configured to scan the image above a region of the substrate. In claim 1,
The apparatus, wherein the first radiation beam is polarized. In claim 22,
The apparatus, wherein the polarization is circular. In claim 1,
The apparatus wherein the axis forms a normal to the surface of the substrate and an incident angle Φ, and 0 ≦ Φ <90 °. In claim 24,
The incident angle Φ is equal to or near the Brewster angle,
The apparatus, wherein the second radiation beam is p-polarized with respect to the substrate. In claim 25,
The substrate is a single crystal semiconductor;
The apparatus, wherein the incident angle Φ is between 50 ° and 80 °. In claim 1,
The substrate includes a lattice pattern;
The apparatus, wherein the image is oriented at 45 ° with respect to the grid pattern. A method for heat treating one or more regions of a substrate, comprising:
a. Generating a continuous radiation beam having a wavelength capable of heating the region; and b. Scanning the radiation above the one or more regions in a scanning direction such that each point in the one or more regions receives an amount of thermal energy that can process each of the one or more regions. . In claim 28,
The substrate is a single crystal;
The method wherein step b is performed such that at each point of the one or more regions, the image has a dwell time between microseconds and milliseconds. In claim 29,
The one or more regions include integrated circuits;
The method wherein the radiation of step b forms an image having an area of 1 cm or less perpendicular to the scanning direction. In claim 28,
The continuous radiation beam has a first profile; and
c. The method further includes altering the continuous radiation beam to form a second profile. In claim 31,
The step c modifies the continuous radiation beam so that the second profile forms an image having a substantially uniform intensity on the substrate. In claim 28,
c. The method further comprises attenuating the continuous radiation beam to maintain the one or more regions at a selected temperature. In claim 28,
The continuous radiation beam has an output power; and
c. Changing the output power to further maintain the one or more regions at a selected temperature. In claim 28,
c. The method further comprising the step of forming a line image. In claim 35,
d. The method further comprises aligning the length of the line image relative to a plane defined by an axis associated with the beam of incident radiation and the beam of reflected radiation. In claim 35,
d. The method further comprises forming the line image by reflecting the radiation beam from a conical mirror. In claim 35,
The line image has a length L1 and a width L2, and
d. A method further comprising changing at least the length and the width. In claim 28,
c. Measuring the radiation reflected from the area of the substrate. In claim 28,
c. Measuring the temperature of the region of the substrate. In claim 40,
The step c further includes
I. Measuring the radiation emitted from the substrate in two different spectral bands. In claim 40,
d. Using each detector array to image a common area of the substrate in a different spectral band; and e. Comparing each output signal from the detector array to determine a maximum temperature point in the common region and a temperature at the maximum temperature point. In claim 28,
The method wherein the radiation beam is polarized. In claim 43,
c. The method further comprises rotating the polarization of the radiation beam by a quarter wavelength. In claim 43,
c. Changing the first radiation beam to further form a circularly polarized beam of radiation. In claim 28,
The radiation beam is p-polarized with respect to the substrate;
c. Irradiating the substrate with the radiation beam at an angle equal to or near a Brewster angle. In claim 28,
The substrate is a single crystal semiconductor;
The radiation beam is p-polarized, and
c. Irradiating the substrate with the radiation beam at an incident angle Φ of 50 ° to 80 °. In claim 28,
The step b is performed in one of a cow plow pattern, a spiral pattern, and an alternating raster pattern. In claim 28,
c. The method further comprises changing the polarization of the first radiation beam to maintain the substrate at a selected temperature. In claim 28,
Performing step b at a variable rate and maintaining the substrate at a selected temperature. In claim 28,
The method wherein the wavelength of the first radiation beam is 9.4 to 10.8 μm. In claim 28,
Step b includes the following steps to minimize the change in the radiation reflected from the substrate:
i. Scanning a continuous beam of radiation above the substrate;
ii. The change in the reflected radiation is measured over a range of incident angles of the continuous first radiation beam to determine an optimum angle of incidence corresponding to at least the smallest change in the amount of reflected radiation. Steps, and iii. Scanning the optimum incident angle or the vicinity thereof and heat-treating the one or more regions. In claim 28,
Step b includes the following steps in order to minimize the change in maximum temperature generated on the substrate:
i. Forming an image from the continuous radiation beam;
i. Scanning the image above the substrate;
iii. Measuring a change in maximum temperature formed at different positions on the substrate with respect to each incident angle over a range of incident angles, and determining an optimum incident angle corresponding to at least a point where the amount of change in the maximum temperature is the smallest. And iv. Scanning the optimum incident angle or the vicinity thereof and heat-treating the one or more regions. In claim 28,
The substrate is crystalline, and
The step b scans the image in a direction that minimizes the formation of sliding surfaces on the substrate. In claim 54,
The substrate has a crystallographic axis;
The step b scans the image in a direction along one of the crystal axes. In claim 28,
The one or more regions have a patterned shape; and
In addition, it includes the following steps:
c. Forming a line image using the continuous radiation beam; and d. Irradiating the substrate with the continuous radiation beam at an angle of incidence using the line image at an image angle with respect to the patterned shape. In claim 56,
The method wherein the angle of incidence and the image angle are selected to minimize temperature changes in the one or more regions. In claim 57,
The substrate is crystalline, and
e. A method of selecting a scanning direction to minimize the formation of sliding surfaces on the substrate. In claim 17,
The diagnostic system includes a detector;
The apparatus, wherein the detector is arranged to observe the heated substrate at a Brewster angle relative to the wavelength used for the detector and film present on the substrate. In claim 59,
The diagnostic system receives and measures radiation having a wavelength of 0.5 to 0.8 μm. In claim 59,
The diagnostic system receives and measures radiation having a wavelength of 3-11 μm. In claim 17,
The diagnostic system includes a detector array;
The apparatus wherein the detector array is arranged to observe the heated substrate at a Brewster angle relative to the wavelength used for the detector and film present on the substrate. In claim 62,
The diagnostic system receives and measures radiation having a wavelength of 0.5 to 0.8 μm. In claim 62,
The diagnostic system receives and measures radiation having a wavelength of 3-11 μm. In claim 1,
A beam forming system for reducing the radiation beam to a small size on the substrate;
A radiation monitor adjacent to the stage, arranged to receive and measure radiation reflected from the substrate;
A scanning system configured to scan the small-sized radiation beam over the substrate in a limited area including one or more chips;
Including
The apparatus wherein the radiation monitor receives radiation indicative of a change in reflectance in the limited area. In claim 1,
A beam forming system for reducing the radiation beam to a small size on the substrate;
A radiation monitor adjacent to the stage, arranged to receive and measure radiation reflected from the substrate;
A scanning system configured to scan the small-sized radiation beam over the substrate in a limited area including one or more chips;
Including
The sized radiation beam is incident on the substrate at a Brewster angle with respect to the film present on the substrate,
The apparatus wherein the radiation monitor receives radiation indicative of a change in reflectance in the limited area. In claim 1,
The diagnostic system further includes:
A detector located on the substrate and a detector arranged to observe a heated region of the substrate at a Brewster angle relative to the wavelength used for the film;
A scanning system that scans the second radiation beam over the substrate in a limited area comprising one or more chips;
Including
The apparatus, when the second radiation beam is scanned over a limited area of the substrate, the detector receives radiation indicative of a temperature change caused by the second radiation beam. In claim 67,
The diagnostic system employs a wavelength of 0.5 to 0.8 μm. In claim 67,
The diagnostic system employs a wavelength of 3 to 11 μm. In claim 1,
The diagnostic system further includes:
A detector located on the substrate and a detector arranged to observe a heated region of the substrate at a Brewster angle relative to the wavelength used for the film;
In a limited area including one or more chips, the second radiation beam is projected above the substrate at a Brewster angle with respect to the wavelength of the second radiation beam and the film present on the substrate. A scanning system for scanning;
Including
The apparatus receives radiation indicative of a temperature change caused by the second radiation beam when the scanning system scans over a limited area of the substrate. In claim 70,
The diagnostic system employs a wavelength of 0.5 to 0.8 μm. In claim 70,
The diagnostic system employs a wavelength of 3 to 11 μm. In claim 1,
The diagnostic system further includes:
A detector array arranged to observe a heated region of the substrate at a Brewster angle relative to the wavelength used for the detector and film present on the substrate;
A scanning system that scans the second radiation beam over the substrate in a limited area comprising one or more chips;
Including
The apparatus, when the second radiation beam is scanned over the limited area, the detector receives radiation indicative of a temperature change caused by the second radiation beam. In claim 1,
A beam positioning system that impinges the second radiation beam on the substrate at a Brewster angle relative to a film present on the substrate;
The diagnostic system includes:
A detector array arranged to observe a heated region of the substrate at a Brewster angle relative to the wavelength used for the detector and the film present on the substrate;
A scanning system that scans the second radiation beam over the substrate in a limited area comprising one or more chips;
Including
The apparatus, when the second radiation beam is scanned over a limited area of the substrate, the detector receives radiation indicative of a temperature change caused by the second radiation beam. In claim 46,
The apparatus wherein the radiation beam is generated by a laser diode array. In claim 75,
The wavelength of the radiation beam from the laser diode array is 0.6 to 1.5 μm.

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